Motor operated compressor

ABSTRACT

An electric compressor includes a first scroll, a second scroll engaged with the first scroll and configured to form a compression chamber between portions of the second scroll and the first scroll during orbiting motion of the second scroll relative to the first scroll, and a frame fixed on an opposite side of the second scroll from the first scroll. A back-pressure space is formed between the frame and the second scroll, and pressure in the back-pressure space pushes the second scroll toward the first scroll. A back-pressure passage connects the compression chamber and the back-pressure space, and a valve member is disposed in the back-pressure passage and selectively blocks movement of a fluid from the back-pressure space to the compression chamber.

CROSS-REFERENCE TO RELATED APPLICATION

Pursuant to 35 U.S.C. § 119(a), this application claims the benefit of earlier filing date and right of priority to Korean Application No. 10-2018-0014800, filed on Feb. 6, 2018, the contents of which is incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present disclosure relates to a compressor and, more particularly, to a motor-operated compressor driven by a motor.

Background of the Invention

Generally, compressors for compressing a refrigerant in automotive air conditioning systems have been developed in various forms. Recently, motor-operated compressors (or electric compressors) driven by electricity using motors have been actively developed as automotive parts tend to become electronic/electric components.

Among several electric compressing schemes, a scroll compressing scheme suitable for a high compression ratio operation is largely applied. In the scroll type electric compressor, a motor part configured as a rotary motor is installed in a closed casing, a compressing part including a fixed scroll and an orbiting scroll is installed on one side of the motor part, and the motor part and the compressing part are connected by a rotary shaft and a rotational force from the motor part is transferred to the compressing part. The rotational force transferred to the compressing part causes the orbiting scroll to pivot relative to the fixed scroll to form a pair of two compression chambers each including a suction chamber, an intermediate pressure chamber, and a discharge chamber so that a refrigerant is sucked into both compression chambers, and compressed and simultaneously discharged.

The related art electric compressor as described above is known to be based on a scheme in which oil is separated from the refrigerant discharged from the compression chamber to a discharge space, a portion of the separated oil is guided to a back-pressure space provided on a rear surface of the orbiting scroll, and the orbiting scroll is supported toward the fixed scroll by pressure of the oil. This is disclosed in Related art 1 (Japanese Patent Laid-Open Publication No. 2010-14108, publication date: 2010 Jan. 21) and Related art 2 (Korean Patent Laid-open Publication No. 10-2017-0139394, Publication date: 2017 Dec. 19).

Also, Related art 3 (Korean Patent Laid-Open Publication No. 10-2013-0041740, published on Apr. 25, 2013) discloses a technique of forming a back-pressure hole at an orbiting scroll to bypass a portion of a refrigerant compressed in the compression chamber to a back-pressure space to support a rear surface of the orbiting scroll.

Such a technique is well known in the art and may be referred to as an intermediate pressure back pressure system.

However, in the case of the related art intermediate pressure back pressure scheme, if pressure of an intermediate pressure chamber is lower than pressure of a back-pressure space, a refrigerant (or/and oil) of the back-pressure space may flow back to the intermediate chamber through a back-pressure hole due to a pressure difference and the refrigerant flowing back to the intermediate pressure chamber forms a relatively high pressure in the intermediate pressure chamber, causing an over-compression.

When the pressure in the intermediate pressure chamber is lower than the pressure in the back-pressure space, the refrigerant (or the oil) in the back-pressure space flows back to the intermediate pressure chamber through the back-pressure hole by the pressure difference, There is a problem that the refrigerant flowing backward to the intermediate pressure chamber forms a high pressure relative to the pressure of the refrigerant compressed in the intermediate pressure chamber, causing excessive compression loss.

In addition, in the related art intermediate pressure back pressure system, the back-pressure space interworks with the intermediate pressure chamber and thus is not uniformly maintained, failing to stably support the orbiting scroll. As a result, a behavior of the orbiting scroll becomes unstable to cause the refrigerant in the compression chamber to leak.

SUMMARY OF THE INVENTION

Therefore, an aspect of the detailed description is to provide an electric compressor in which a pressure of a compression chamber and a pressure of a back-pressure space are uniformly maintained in a scheme in which a portion of a refrigerant compressed in an intermediate pressure chamber of a compression chamber is induced to a back-pressure space to support an orbiting scroll by the pressure of the back-pressure space.

Another aspect of the detailed description is to provide an electric compressor in which a refrigerant and oil are restrained from flowing back to an intermediate pressure chamber from a back-pressure space due to a pressure difference between the intermediate pressure chamber and the back-pressure space.

Another aspect of the detailed description is to provide an electric compressor in which a refrigerant and oil are restrained from flowing back to an intermediate pressure chamber from a back-pressure space by selectively opening and closing a flow path between the intermediate pressure chamber and the back-pressure space.

Another aspect of the detailed description is to provide an electric compressor in which a valve for selectively opening and closing a flow path between the intermediate pressure chamber and the back-pressure space is provided and the occurrence of abnormal noise is suppressed during a process of opening and closing a compression chamber and the back-pressure space.

Another aspect of the detailed description is to provide an electric compressor in which a valve is uniformly moved during a process of opening and closing a compression chamber and a back-pressure space.

Another aspect of the detailed description is to provide an electric compressor in which a valve for selectively opening and closing a flow path between the intermediate pressure chamber and the back-pressure space is provided and, here, the valve can be easily assembled.

Another aspect of the detailed description is to provide an electric compressor in which a compression chamber and a back-pressure space may be connected at a shortest distance to facilitate manufacturing of the electric compressor.

To achieve these and other advantages and in accordance with the purpose of this specification, as embodied and broadly described herein, there is provided an electric compressor in which a back-pressure space is provided on a rear surface of an orbiting scroll to form a back pressure in a direction toward a fixed scroll, a passage connecting a compression chamber between the fixed scroll and the orbiting scroll and the back-pressure space is formed, and a valve is provided to open and close the passage.

The orbiting scroll may be supported by a frame coupled to the fixed scroll, and the passage may penetrate through the fixed scroll and the frame.

The passage may penetrate through the orbiting scroll.

The valve may be configured as a piston valve, and a communication recess may be formed to be connected to an outer circumferential surface of the valve and one side surface to open the passage.

To achieve these and other advantages and in accordance with the purpose of this specification, as embodied and broadly described herein, an electric compressor includes: a first scroll; a second scroll engaged with the first scroll to make an orbiting motion to form a compression chamber with the first scroll; a frame fixed in a radial direction on the opposite side of the first scroll with the second scroll interposed therebetween, forming a back-pressure space with the second scroll so that the second scroll is supported in a direction toward the first scroll by pressure of the back-pressure space; a back-pressure passage connecting the compression chamber and the back-pressure space; and a valve member provided at the back-pressure passage and blocking movement of a fluid from the back-pressure space to the compression chamber.

The back-pressure passage may include a back-pressure hole in which one end communicates with the compression chamber and the other end communicates with the back-pressure space and a valve accommodation recess communicating with the back-pressure hole and accommodating the valve member, and the valve member is configured as a check valve slidably moving inside the valve accommodation recess according to a pressure difference between the compression chamber and the back-pressure space.

The valve member may include a valve portion opening the back-pressure passage at a first position and closing the back-pressure passage at a second position.

The valve portion may have a first side surface, a second side surface, and a circumferential surface connecting the first side surface and the second side surface, and a diameter of the first side surface and a diameter of the second side surface may be greater than an inner diameter of the back-pressure hole and smaller than an inner diameter of the valve accommodation recess.

The electric compressor may further include: an opening and closing surface formed on the first side surface of the valve portion such that at least a portion thereof is flat and formed to have a diameter greater than the inner diameter of the back-pressure hole to block the back-pressure hole at the second position; a support surface formed on the second side surface of the valve portion and formed to contact a side surface of the valve accommodation recess; and a communication recess formed to a predetermined depth on the support surface, opened to the circumferential surface of the valve portion, and at least partially overlapping a back-pressure hole facing the second side surface.

The valve member may further include: at least one guide portion guiding the valve portion from the first position to the second position, and the at least one guide portion may extend in a radial direction toward an inner circumferential surface of the valve accommodation recess on the circumferential surface of the valve portion.

The at least one guide portion may protrude in a radial direction from a portion excluding at least a portion of the circumferential surface of the valve portion, and the communication recess may be opened to the circumferential surface of the valve portion positioned between the at least one guide portion.

The communication recess may have at least two end portions opened to the circumferential surface of the valve portion.

The guide portion may be provided in plurality, and the plurality of guide portions may be formed at equal intervals along a circumferential direction.

The at least one guide portion may be a single guide portion, and a subtended angle of the guide portion may be greater than or equal to approximately 180°. The term “approximately” when used throughout this specification and claims refers to an amount, value, or dimension within normal machining and/or assembly tolerances.

The at least one guide portion may have a thickness which is approximately equal to or smaller than a thickness of the valve portion.

A guide recess may be formed on an inner circumferential surface of the valve accommodation recess so that the at least one guide portion is inserted into the guide recess so as to be restrained in a circumferential direction.

An elastic member may be further provided on any one of both sides of the valve member in a movement direction.

The back-pressure passage may include: a first back-pressure hole provided at the first scroll and communicating with the compression chamber; and a second back-pressure hole provided at the frame and communicating with the back-pressure hole, wherein the first back-pressure hole and the second back-pressure hole communicate with each other and a valve accommodation recess accommodating the valve may be formed on a surface where the first back-pressure hole is formed or a surface where the second back-pressure hole is formed.

The back-pressure passage may be formed to penetrate through the second scroll facing the back-pressure space, a valve accommodation recess may be formed in the middle of the back-pressure passage, a stopper member limiting movement of the valve member may be inserted and coupled to the valve accommodation recess, and the stopper member may have a back-pressure hole forming the back-pressure passage.

To achieve these and other advantages and in accordance with the purpose of this specification, as embodied and broadly described herein, an electric compressor includes: a compression chamber formed between a first scroll and a second scroll and moving from an outer side to an inner side so as to be reduced in volume thereof to compress a fluid; a back-pressure space formed between the second scroll and a frame supporting the second scroll and supporting the second scroll toward the first scroll; a back-pressure flow path connecting the compression chamber and the back-pressure space; a valve accommodation recess provided in the middle of the back-pressure flow path; and a check valve provided at the valve accommodation recess and blocking the back-pressure flow path when a pressure of the back-pressure space is higher than a pressure of the compression chamber.

The check valve may include a valve portion formed with a diameter greater than an inner diameter of the back-pressure flow path and smaller than an inner diameter of the valve accommodation recess, at least a portion of one side surface of the valve portion may be formed to be flat so as to be in close contact with one side of the valve accommodation recess to block the back-pressure flow path, and the other side surface of the valve portion may have a communication recess to open the back-pressure flow path in a state in which the other side surface of the valve portion is in close contact with the other side of the valve accommodation recess.

The check valve may further include: at least one guide portion in slidable contact with an inner circumferential surface of the valve accommodation recess to guide the valve portion, and the at least one guide portion may protrude from a circumferential surface of the valve portion along a circumferential direction.

In the electric compressor according to the present disclosure, a back-pressure passage is formed between the compression chamber and the back-pressure space and a check valve is provided in the middle of the back-pressure passage, whereby the refrigerant and oil may be restrained from flowing back to the compression chamber when a pressure of the compression chamber is temporarily low such as when the compression is re-started.

Further, since the communication recess is formed on one side surface of the check valve, a wide flow path area may be secured. As a result, the refrigerant and oil may quickly move from the intermediate pressure chamber to the back-pressure space, effectively ensuring a back pressure.

Further, according to the present disclosure, since a flow path between the compression chamber and the back-pressure space is selectively opened and closed, pressure in the compression chamber and pressure in the back-pressure space are restrained from becoming unstable, thus stabilizing the behavior of the orbiting scroll to uniformly compress the refrigerant.

Further, in the present disclosure, an elastic member is added to one side of the check valve that opens and closes a flow path between the compression chamber and the back-pressure space to suppress or minimize the occurrence of abnormal noise during the process of opening and closing the check valve.

Further, according to the present disclosure, the check valve that opens and closes a flow path between the compression chamber and the back-pressure space is guided by the guide protrusion and the guide recess to make the behavior of the valve uniform, whereby the position of the passage may be constant, increasing reliability of the check valve.

Further, according to the present disclosure, since an accommodation recess of the check valve for opening and closing a flow path between the compression chamber and the back-pressure space may be formed as part of the back-pressure passage, the check valve may be easily assembled.

Further, in the present disclosure, since a passage connecting the compression chamber and the back-pressure space is formed at the orbiting scroll forming the back-pressure space, a distance between the compression chamber and the back-pressure space may be minimized, facilitating manufacturing of the electric compressor.

Further scope of applicability of the present application will become more apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the scope of the invention will become apparent to those skilled in the art from the detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments and together with the description serve to explain the principles of the invention.

In the drawings:

FIG. 1 is a cross-sectional view illustrating the inside of an electric compressor according to the present disclosure;

FIG. 2 is a plan view illustrating a state in which a fixed side wrap and an orbiting side wrap are engaged in a compression mechanism part according to FIG. 1;

FIG. 3 is a cross-sectional view illustrating an example in which a back-pressure hole is formed to penetrate through a fixed scroll and a frame according to the present disclosure;

FIGS. 4A and 4B are front and rear perspective views of a check valve according to the present disclosure, respectively;

FIGS. 5A and 5B are front and rear cross-sectional views illustrating states in which a check valve is inserted into a valve accommodation recess according to the present disclosure, respectively;

FIGS. 6A to 8D illustrate other embodiments of a check valve according to the present disclosure, in which FIGS. 6A and 6B illustrate a case in which a single guide portion is provided, FIGS. 7A and 7B illustrate a case in which two guide portions are provided, and FIGS. 8A to 8D illustrate a communication recess;

FIGS. 9A and 9B illustrate an operation of a check valve according to the present disclosure, in which FIG. 9A illustrates a state in which an electric compressor normally operates and FIG. 9B illustrates an operation when the electric compressor starts;

FIG. 10 is a perspective view illustrating another embodiment of a check valve according to the present disclosure;

FIGS. 11A and 11B are cross-sectional views illustrating an example in which a check valve has an elastic member according to the present disclosure;

FIGS. 12 and 13 are cross-sectional views illustrating other embodiments of a check valve and a valve accommodation recess according to the present disclosure; and

FIG. 14 is a cross-sectional view illustrating an example in which a back-pressure hole is formed to penetrate through an orbiting scroll.

DETAILED DESCRIPTION OF THE INVENTION

Description will now be given in detail of the exemplary embodiments, with reference to the accompanying drawings. For the sake of brief description with reference to the drawings, the same or equivalent components will be provided with the same reference numbers, and description thereof will not be repeated.

Hereinafter, an electric compressor according to an embodiment of the present disclosure will be described in detail with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view illustrating the inside of an electric compressor according to the present disclosure, and FIG. 2 is a plan view illustrating a state in which a fixed side wrap and an orbiting side wrap are engaged in a compression mechanism part according to FIG. 1.

As illustrated FIGS. 1 and 2, a low-pressure type electric scroll compressor (hereinafter, referred to as an “electric compressor”) according to the present embodiment includes a driving motor 103, which is a motor part, and a compression mechanism part 105 compressing a refrigerant using a rotational force of the driving motor 103.

The compressor casing 101 includes an intake port 111 a to which a suction pipe is connected and an exhaust port 121 a to which a discharge pipe is connected. A suction space S1 is formed at the intake port 111 a, and a discharge space S2 is formed at the exhaust port 121 a, respectively. The driving motor 103 is installed in the suction space S1, and the compressor of the present embodiment is a low-pressure compressor.

The compressor casing 101 includes a main housing 110 in which the driving motor 103 is installed and a rear housing 120 coupled to an open rear end of the main housing 110. An internal space of the main housing 110 forms the suction space S1 together with one side of the compression mechanism part 105 and an internal space of the rear housing 120 forms the discharge space S2 together with the other side of the compression mechanism part 105.

The main housing 110 has a cylindrical portion 111 having a cylindrical shape, a closed portion 112 integrally extends from a front end of the cylindrical portion 111 and is closed, and an opening 113 is formed at a rear end of the cylindrical portion 111.

Meanwhile, the driving motor 103 forming a motor part is press-fit and coupled inside the main housing 110. The driving motor 103 includes a stator 131 fixed inside the main housing 110 and a rotor 132 positioned inside the stator 131 and rotated by an interaction with the stator 131.

The stator 131 is shrink-fit and fixed to an inner circumferential surface of the main housing 110. A rotary shaft 133 is press-fit and coupled to an inner circumferential surface of the rotor 132.

The rotary shaft 133 is coupled to the center of the rotor 132 and a rear end thereof facing the compression mechanism part 105 is cantilevered to the frame 140 and the fixed scroll 150 as described later.

Meanwhile, in the scroll compressor according to the present embodiment, the orbiting scroll coupled to the rotary shaft is supported by the frame and is pivotally moved relative to the fixed scroll, thereby forming the compression mechanism part.

As illustrated in FIGS. 1 and 2, the compression mechanism part 105 includes a frame 140, a fixed scroll (hereinafter, referred to as a “first scroll”) 150 supported by the frame 140, and an orbiting scroll (hereinafter referred to as a “second scroll”) 160 provided between the frame 140 and the first scroll 150 and making an orbiting motion.

The frame 140 is coupled to a front side opening 113 of the main housing 110. The first scroll 150 is fixedly supported on a rear surface of the frame 140, and the second scroll 160 is pivotably supported on the rear surface of the frame 140 to make an orbiting motion between the first scroll 150 and the frame 140. The second scroll 160 is coupled in an off-centered manner to the rotary shaft 133 coupled to the rotor 132 of the driving motor 103 and makes an orbiting motion relative to the first scroll 150, forming a pair of two compression chambers V including a suction chamber, an intermediate pressure chamber, and a discharge chamber.

The frame 140 includes a disk plate portion 141 having a disk shape and a frame side wall portion 142 protruding from a rear side surface of the frame disk plate portion 141 toward the first scroll 150 and allowing a side wall portion 152 of the first scroll 150 (to be described hereinafter) is coupled.

A frame thrust surface 143 is formed on an inner side of the frame side wall portion 142. The second scroll 160 is mounted and supported in an axial direction on the frame thrust surface 143. A back-pressure space 144 is formed at the center of the frame thrust surface 143 and filled with a portion of the refrigerant compressed in the compression chamber V and oil to support the rear surface of the second scroll 160. Accordingly, a pressure of the back-pressure space 144 corresponds to an immediate pressure between a pressure of the suction space S1 and a final pressure (i.e., discharge space) of the compression chamber V. This will be described later together with a check valve opening and closing the of compression chamber and the back-pressure space.

A frame shaft hole 145 through which the rotary shaft 133 passes is formed in the middle of the back-pressure space 144 and a first bearing (not shown) is provided on an inner circumferential surface of the frame shaft hole 145. The first bearing may be formed of a bush bearing, but in some cases, it may be a ball bearing. Here, the bush bearing is less expensive than the ball bearing, and thus, the bush bearing is advantageous in terms of cos, and also, the bush bearing is easily assembled and reduced in weight and noise.

The back-pressure space 144 may be sealed by a first sealing member 191 provided on a thrust surface between the frame 140 and the second scroll 160 and a second sealing member 192 disposed between an inner circumferential surface of the frame 140 and an outer circumferential surface of the rotary shaft 133. However, the second sealing member 192 may be omitted in some cases.

Meanwhile, the first scroll 150 may be fixedly coupled to the frame 140 or may be press-fit and fixed to the casing 110.

In the first scroll 150, a fixed scroll disk plate portion (hereinafter, referred to as a ‘fixed side disk plate portion’) 151 is formed to have a substantially disk shape, and a fixed scroll side wall portion (hereinafter, referred to as a ‘first side wall portion’) 152 coupled to the side wall portion 142 of the frame 140 is formed at the edge of the fixed side disk plate portion 151. A fixed side wrap 153 engaged with an orbiting side wrap 162 (to be described later) to form the compression chamber V is formed on a front side of the fixed side disk plate portion 151. The fixed side wrap 153 will be described later together with the orbiting side wrap 162. The term “substantially” when used throughout this specification and claims refers to a shape, dimension, value, or other characteristic that meets the description within normal material, machining and/or assembly tolerances.

A suction flow path (not shown) is formed on one side of the first side wall portion 152 so that the suction space S1 and a suction chamber (not shown) communicate with each other, and a discharge port 155 is formed at a central portion of the fixed side disk plate portion 151 and communicates with a discharge chamber so that the compressed refrigerant is discharged to the discharge space S2. Only one discharge port 155 may be formed to communicate with both a first compression chamber V1 and a second compression chamber V2 (to be described later) or a first discharge port 155 a and a second discharge port 155 b may be formed to communicate with the first compression chamber V1 and the second compression chamber V2, respectively.

The second scroll 160 may be provided between the frame 140 and the first scroll 150 and may be coupled to the rotary shaft 133 in an off-centered manner so as to be pivotable.

In the second scroll 160, an orbiting scroll disk plate portion (hereinafter, referred to as an “orbiting side disk plate portion”) 161 is formed to have a substantially disk shape and an orbiting side wrap 162 engaged with the fixed side wrap 153 to form a compression chamber is formed on a rear side of the orbiting side disk plate portion 161. The orbiting side wrap 162 may be formed in an involute shape together with the fixed side wrap 153 or may be formed in various other shapes.

The orbiting side wrap 162 may have a shape in which a plurality of circular arcs having different diameters and starting points are connected to each other, and the outermost curve may have a substantially oval shape having a longer axis and a shorter axis. This may also be the same with the fixed side wrap 153.

A rotary shaft coupling portion 163 may be formed in a penetrating manner at a central portion of the orbiting side disk plate portion 161. The rotary shaft coupling portion 163 may form an inner end portion of the orbiting side wrap 162 and an eccentric portion 133 a of the rotary shaft 133 (to be described later) may be rotatably inserted and coupled to the rotary shaft coupling portion 163. An outer circumferential portion of the rotary shaft coupling portion 163 may be connected to the orbiting side wrap 162 to form the compression chamber V together with the fixed side wrap 153 during a compressing process.

The rotary shaft coupling portion 163 is formed to have a height that overlaps on the same plane as the orbiting side wrap 162 so that the eccentric portion 133 a of the rotary shaft 133 may be disposed at a height that overlaps on the same plane with the orbiting side wrap 162. Accordingly, a repulsive force and a compressive force of the refrigerant are applied to the same plane with respect to the orbiting side disk plate portion so as to be canceled out, and thus, tilting of the second scroll 160 due to the action of the compressive force and the repulsive force may be prevented.

The rotary shaft coupling portion 163 has a concave portion 163 a which is engaged with a protrusion 153 a of the fixed side wrap 153 (to be described later) at an outer circumferential portion facing an inner end of the fixed side wrap 153, and an increased portion 163 b is formed on one side of the concave portion 163 a and is formed on an upstream side along a formation direction of the compression chamber V, and a thickness of the increased portion 163 b is increased from an inner circumferential portion to an outer circumferential portion of the rotary shaft coupling portion 163.

An increased portion 163 b is formed on one side of the portion 163 a along the forming direction of the compression chamber V to increase the thickness from the inner circumferential portion to the outer circumferential portion of the rotary shaft coupling portion 163 on the upstream side. Thus, a compression path of the first compression chamber V1 immediately before discharging is lengthened, and as a result, a compression ratio of the first compression chamber V1 may be increased to be close to a compression ratio of the second compression chamber V2.

A circular arc compression surface 163 c having a circular arc shape is formed on the other side of the concave portion 163 a. A diameter of the circular arc compression surface 163 c is determined by a thickness of an inner end portion of the fixed side wrap 153 (i.e., a thickness of a discharge end) and an orbiting radius of the orbiting side wrap 162. Here, when the thickness of the inner end portion of the fixed side wrap 153 is increased, the diameter of the circular arc compression surface 163 c is increased. Accordingly, a thickness of the orbiting side wrap around the circular arc compression surface 163 c is also increased to ensure durability, and since a compression path is lengthened, a compression ratio of the second compression chamber V2 may also be increased.

A protrusion 153 a protruding toward an outer circumferential portion of the rotary shaft coupling portion 163 is formed near an inner end portion (suction end or start end) of the fixed side wrap 153 corresponding to the rotary shaft coupling portion 163, and a contact portion 153 b may protrude from the protrusion 153 a so as to be engaged with the concave portion 163 a. That is, the inner end portion of the fixed side wrap 153 may have a thickness greater than those of other portions. As a result, wrap strength of the inner end portion, which is subjected to the greatest compressive force in the fixed side wrap 153, may be improved to improve durability.

The compression chamber V is formed between the fixed side disk plate portion 151 and the fixed side wrap 153 and between the orbiting side wrap 162 and the orbiting side disk plate portion 161, and the suction chamber, the intermediate pressure chamber, and the discharge chamber may be continuously formed according to a movement direction of the wraps.

The compression chamber V may include the first compression chamber V1 formed between an inner side surface of the fixed side wrap 153 and an outer side surface of the orbiting side wrap 162 and a second compression chamber V2 formed between an outer side surface of the fixed side wrap 153 and an inner side surface of the orbiting side wrap 162. That is, the first compression chamber V1 is formed between two contact points P11 and P12 formed as the inner side surface of the fixed side wrap 153 and the outer side surface of the orbiting side wrap 162 are in contact with each other, and the second compression chamber V2 is formed between two contact points P21 and P22 formed as the outer side surface of the fixed side wrap 153 and the inner side surface of the orbiting side wrap 162.

Here, in the first compression chamber V1 immediately before discharging, when an angle having a greater value among angles formed by two lines connecting the center O of the eccentric portion, i.e., the center O of the rotary shaft coupling portion, and the two contact points P11 and P12 is a, a may be smaller than 360° (α<360°) at least immediately before starting discharging and a distance l between normal vectors at the two contact points P11 and P12 has a value greater than 0.

As a result, compared with a case where the first compression chamber immediately before discharging includes a fixed side wrap and an orbiting side wrap forming an involute curve, the compression chamber has a smaller volume, and thus, both a compression ratio of the first compression chamber V1 and a compression ratio of the second compression chamber V2 may be improved.

In the figure, reference numeral 137 denotes a balance weight.

The scroll compressor according to the embodiment described above operates as follows.

That is, when power is applied to the driving motor 103, the rotary shaft 133 rotates together with the rotor 132 to transmit a rotational force to the second scroll 160, and the second scroll 160 makes an orbiting motion by an anti-rotation mechanism, and accordingly, the compression chamber V may be continuously moved toward the center side, while being reduced in volume.

The refrigerant then flows into the suction space S1 through the suction port 111 a and the refrigerant introduced into the suction space S1 passes through a flow path formed on an outer circumferential surface of the stator 131 and an inner circumferential surface of the main housing 110 or an air gap between the stator 131 and the rotor 132 so as to be sucked to the compression chamber V through the suction flow path 154.

Here, a portion of the refrigerant sucked into the suction space S1 through the intake port 111 a first comes into contact with the closed portion 112, which is a front side surface of the main housing 110, before passing through the driving motor 103. Accordingly, the closed portion 112 is heat-exchanged with and cooled by the cold suction refrigerant to cool an inverter module (not shown) attached to the outer side surface of the main housing 110.

The refrigerant sucked into the compression chamber V through the suction space S1 is compressed by the first scroll 150 and the second scroll 160 and is discharged to the discharge space S2 through the discharge port 155. In the discharge space S2, the refrigerant and oil are separated and the refrigerant is discharged to a refrigerating cycle through the exhaust port 121 a, while the oil gathers at a lower portion of the discharge space S2.

As described above, in the process of compressing the refrigerant in the compression chamber between the first scroll and the second scroll, the second scroll as the orbiting scroll may be pushed toward the frame due to pressure of the compression chamber. In this case, a gap may be formed between the first scroll and the second scroll to cause a leakage between the compression chambers. This phenomenon may be suppressed by pressure of the back-pressure space formed on the rear side of the second scroll, that is, between the second scroll and the frame.

As described above, in the back-pressure space, a portion of the refrigerant compressed in the middle of the compression chamber, that is, in the intermediate pressure chamber, is supplied to the back-pressure space through the back-pressure hole, and thus, the pressure in the back-pressure space forms the intermediate pressure. Therefore, the second scroll is pushed toward the first scroll by the force of the pressure in the back-pressure space, so that the second scroll may be prevented from moving away from the first scroll. Here, the back-pressure hole may be formed to penetrate through the first scroll and the frame, or may be formed to penetrate through the second scroll. FIG. 3 is a cross-sectional view illustrating an example in which the back-pressure hole is formed to penetrate through the first scroll and the frame.

As illustrated in FIG. 3, the back-pressure hole 170 may include a first back-pressure hole 171 formed at the first scroll 150 and a second back-pressure hole 172 formed at the frame 140.

A first end 171 a of the first back-pressure hole 171 is open to communicate with the intermediate pressure chamber of the compression chamber V and a second end 171 b of the first back-pressure hole 171 is open to a rear side surface (i.e., a fixed surface in contact with the frame) of the fixed side disk plate portion 151 (That is, a fixing surface in contact with the frame).

A first end 172 a of the second back-pressure hole 172 is open to the front side surface (i.e., a fixed surface in contact with the first scroll) of the frame side wall portion 142 so as to communicate with the second end 171 b of the first back-pressure hole 171 and the second end 172 b of the second back-pressure hole 172 is open to communicate with a side wall surface of the back-pressure space 144. Accordingly, the first back-pressure hole 171 and the second back-pressure hole 172 communicate with each other to connect the compression chamber V and the back-pressure space 144.

When the compression chamber V and the back-pressure space 144 are connected by the back-pressure hole 170 including the first back-pressure hole 171 and the second back-pressure hole 172 as described above, the refrigerant having the intermediate pressure compressed in the compression chamber A moves to the back-pressure space 144 through the back-pressure hole 170 and a back pressure formed by the intermediate pressure refrigerant which moves to the back-pressure space 144 supports the second scroll 1600 in a direction toward the first scroll 150.

However, the pressure in the compression chamber is varied while the compressor operates, stops, and re-starts, and as the pressure in the compression chamber is varied, pressure in the back-pressure space 144 is also changed. For example, at an initial stage of the operation of the compressor or during a saving operation, the pressure in the compression chamber V is not sufficiently increased so the pressure in the intermediate pressure chamber is lower than the pressure in the back-pressure space 144, but when the compressor reaches a normal operation or during a power operation, the pressure in the compression chamber (intermediate pressure chamber) V becomes higher than the pressure in the back-pressure space 144, and this process is repeated. Here, when the pressure in the compression chamber V is higher than the pressure in the back-pressure space 144, the refrigerant (or/and oil) in the compression chamber (intermediate pressure chamber) moves to the back-pressure space 144 through the back-pressure hole 170, generating a normal back pressure, but when the pressure in the compression chamber V is lower than the pressure in the back-pressure space 144, the refrigerant (and/or oil) in the back-pressure space 144 may flow back to the intermediate pressure chamber through the back-pressure hole 170. In this case, the pressure in the intermediate pressure chamber may be increased to degrade compression efficiency due to over-compression.

In view of this, in this embodiment, a valve accommodation recess 175 is formed in the middle of the back-pressure hole 170, and a check valve 180 may be installed to selectively open and close the back-pressure hole 170, while moving between a first position P1 and a second position P2 according to a pressure difference between the compression chamber (intermediate pressure chamber) and the back-pressure space 144. Here, the first position P1 is a position where the back-pressure passage 170 is open, and the second position P2 is a position where the back-pressure passage 170 is closed (blocked).

The valve accommodation recess 175 may be formed in the middle of the first back-pressure hole 171 or the second back-pressure hole 172, i.e., between the first ends 171 a and 172 a and the second ends 171 b and 172 b of the first back-pressure hole 171 or the second back-pressure hole 172. Alternatively, in consideration of processing or assembling, the valve accommodation recess 175 may be formed at the second end 171 b of the first back-pressure hole 171 or the first end 172 a of the second back-pressure hole 172, or a half of the valve accommodation recess 175 may be formed at the second end 171 b of the first back-pressure hole 171 and another half of the valve accommodation recess 175 may be formed at the first end 172 a of the second back-pressure hole 172. Hereinafter, an example in which the valve accommodation recess 175 is formed at the second end 171 b of the first back-pressure hole 171 will be described.

The valve accommodation recess 175 is formed as a cylindrical recess having an inner diameter D2 larger than an inner diameter D1 of the first back-pressure hole 171. Thus, a first valve seat surface 175 a may be formed at an end portion of the valve accommodation recess 175 adjacent to the first scroll 180 such that an opening and closing surface 181 a forming a first side surface in a valve portion 181 of the check valve 180 (to be described later) is detachably attached. The first valve seat surface 175 a may be formed flat or may be stepped so that a sealing surface for increasing a sealing force with respect to the check valve 180 encloses the first back-pressure hole 171.

Also, the other end of the valve accommodation recess 175 is open and an inner diameter D1′ of the second back-pressure hole 172 is formed to be equal to the inner diameter D1 of the first back-pressure hole 171, and thus, a portion excluding the second back-pressure hole 172 is blocked by the front side surface of the frame 140. Accordingly, a second valve seat surface 175 b may be formed in the vicinity of the end of the second back-pressure hole 172 so that a support surface 181 b forming a second side surface of the valve portion 181 of the check valve 180 is detachably attached. Like the first valve seat surface, the second valve seat surface may also be flat or have a sealing surface.

Meanwhile, as described above, the check valve 180 may be configured as a piston valve that moves between the first position P1 and the second position P2 in accordance with a pressure difference between the compression chamber V and the back-pressure space 144 as a whole.

The check valve 180 may include the valve portion 181 substantially opening and closing the back-pressure hole 170 and a guide portion 182 for guiding the valve portion 181 to reciprocate stably.

The valve portion 181 may include a first side surface (opening and closing surface) 181 a, a second side surface (support surface) 181 b, and a circumferential surface connecting the first side surface 181 a and the second side surface 181 b, and may have a short circular bar shape or a disk plate or a disk shape having a predetermined thickness.

A diameter D3 of the first side surface 181 a and a diameter D3′ of the second side surface 181 b may be larger than the inner diameter D1 or D1′ of the back-pressure hole 170 and smaller than the inner diameter D2 of the valve accommodation recess 175. Accordingly, the valve portion 181 communicates the back-pressure hole 170 at the first position P1 and may block the back-pressure hole 170 at the second position P2.

On the first side surface of the valve portion 181, an opening and closing surface 181 a for opening and closing the first back-pressure hole 171 may be formed. The opening surface 181 a may be formed larger than the inner diameter D1 of the first back-pressure hole 171 so as to block the first back-pressure hole 171 at the second position P2. The opening surface 181 a may be formed to be flat on the entire first side surface, or it may be formed flat only at a central portion of the first side surface and may not be formed at the edge thereof.

The second side surface of the valve portion 181 may have the support surface 181 b to be detachably attached to the second valve seat surface 175 b around the second back-pressure hole 172. The support surface 181 b may be formed flat to be in contact with a side surface of the valve 175, i.e., the second valve seat surface 175 b, at the first position P1.

At least one guide portion 182 may be formed. Of course, a plurality of guide portions 182 may be advantageous in terms of stability of the check valve 180. However, if the number of the guide portions 182 is large, the speed of the check valve 180 may be deteriorated due to friction resistance. Therefore, it is necessary to appropriately design the number and a sectional area of the guide portion 182 in consideration of friction resistance.

For example, as illustrated in FIGS. 4A to 5B, three guide portions 182 may be formed. In this case, the guide portions 182 may be formed at an interval of 120 degrees along the circumferential direction.

Further, as illustrated in FIGS. 6A and 6B, only one guide portion 182 may be formed. However, when one guide portion 182 is provided, an included angle (a) on both sides forming the guide portion 182 may be approximately 180° or greater. If the included angle (a) is less than 180°, an opening side angle between both sides of the guide portion 182 is 180° or greater, and as a result, an outer circumferential surface of the guide portion 182 is separated from the inner circumferential surface of the valve accommodation recess 175 and it cannot serve as a valve. Of course, in this case, although the opening side angle between the both side surfaces of the guide portion 182 is 180° or greater, if a depth of the opening side is shallow, the opening and closing surface 181 a may open and close the first back-pressure hole 171. The check valve 180 may then serve as a valve. Nevertheless, the valve portion 181 of the check valve 180 is not constant in its movement in the valve accommodation recess 175 is not uniform in behavior in the valve accommodation recess 175 but fluctuates, causing valve noise or failing to uniformly opening and closing the back-pressure hole to lead to a degradation of the reliability.

Also, as illustrated in FIGS. 7A and 7B, the guide portion 182 may be formed on both sides. In this case, the guide portions 182 may be formed at an equal interval by 180° so as to be balanced when the check valve 180 is moved.

Meanwhile, a communication recess 183 may be formed to be recessed to a predetermined depth at a central portion of the support surface 181 b so that the second back-pressure hole 172 is open even when the support surface 181 b is in contact with the second valve seat surface 175 b. As a result, the area of the flow path of the refrigerant and the oil moving from the intermediate pressure chamber to the back-pressure space 144 may be secured to be large, and the back pressure may be rapidly secured against the orbiting scroll.

The communication recess 183 may be open to a circumferential surface of the valve portion 181 and at least a portion thereof may overlap the second back-pressure hole 172 facing the support surface 181 b. The communication recess 183 may have various shapes. For example, the communication recess 183 may have a T shape as illustrated in FIG. 4B. In this case, three opening ends 183 a may be respectively open between the guide portions 182 to form a kind of communication flow path.

Also, the communication recess 183 may be formed to be open at a circumferential surface of one side of the valve portion 181 and extend to a central portion as illustrated in FIG. 8A, or may be open at a circumferential surface of one side of the valve portion 181, extend to a central portion, and increased from the central portion so as to be larger than the second back-pressure hole 172 as illustrated in FIG. 8B. Alternatively, the communication recess 183 may be formed across both outer circumferential surfaces of the valve portion 181 as illustrated in FIG. 8C, or the entire second side surface 181 b of the valve portion 181 may be stepped so as to be utilized as the communication recess 181 as illustrated in FIG. 8D. In addition, as described above, the communication recess 183 may have any shape as long as it is open at the circumferential surface of the valve portion 181 and communicate with the second back-pressure hole 172.

Meanwhile, the check valve 180 may be formed of a material which is light and lubricous such as plastic, considering that it is a piston valve which is moved by a pressure difference.

Operational effects of the check valve 180 provided in the back-pressure hole in the electric compressor according to the present embodiment as described above are as follows.

That is, as illustrated in FIG. 9A, when the compressor operates normally or the pressure in the intermediate pressure chamber is higher than the pressure in the back-pressure space 144, a portion of the refrigerant compressed in the intermediate pressure chamber V moves toward the valve accommodation recess 175 through the first back-pressure hole 171. Then, the check valve 180 is pushed by the refrigerant flowing from the intermediate pressure chamber toward the back-pressure space 144 through the first back-pressure hole 171, and thus, the first back-pressure hole 171 is opened. The refrigerant moving from the first back-pressure space 144 to the valve accommodation recess 175 moves to the second back-pressure hole 172 through the communication recess 183 between the support surfaces 181 b formed on the second side surface of the check valve 180, and the refrigerant is introduced to the back-pressure space 144 to form a back pressure.

Meanwhile, as illustrated in FIG. 9B, when the compressor is stopped or the pressure in the intermediate pressure chamber is lower than the pressure in the back-pressure space 144, the refrigerant in the back-pressure space 144 flows through the second back-pressure hole 172 into the valve accommodation recess 175. Then, the check valve 180 is pushed by the refrigerant flowing from the back-pressure space 144 to the intermediate pressure chamber through the second back-pressure hole 172, and is moved toward the first back-pressure hole 171. Then, the opening surface 181 a of the check valve 180 is brought into close contact with the first valve seat surface 175 a of the valve accommodation recess 175 to block the first back-pressure hole 171. Then, the refrigerant in the back-pressure space 144 is prevented from flowing back to the intermediate pressure chamber. Thereafter, when the pressure of the compression chamber (intermediate pressure chamber) V increases to a predetermined pressure, the check valve 180 is pushed again in the direction toward the second back-pressure hole 172 to open the back-pressure hole. This sequential process is repeated.

In this manner, even when the compressor is stopped or the pressure in the intermediate pressure chamber is lowered, the pressure when the compressor operates or the pressure of the intermediate pressure chamber may be maintained to be higher than the pressure of the back-pressure space, whereby the second scroll may be restrained from being excessively separated from the first scroll even at initial driving of the compressor. Accordingly, the pressure of the compression chamber is quickly increased to the discharge pressure, improving compressor efficiency.

In addition, even when the pressure of the intermediate pressure chamber is low when the compressor starts to operate or at an initial stage of operation, the refrigerant having a relatively high pressure is prevented from flowing back to the intermediate pressure chamber from the back-pressure space. Thus, pressure pulsation at the intermediate pressure chamber may be suppressed to make the compression process uniform, and over-compression loss made as the pressure in the intermediate pressure chamber is excessively increased may be prevented in advance.

In the above-described embodiment, the thicknesses of the valve portion and the guide portion are equal. However, in some cases, the thickness of the guide portion may be thinner than the thickness of the valve portion. For example, as illustrated in FIG. 10, the thickness of the valve portion 181 is formed to be thicker than the thickness of the guide portion 182 and a stepped surface 182 a may be formed at a portion where the valve portion 181 and the guide portion 182 are in contact with each other. In this case, the thickness of the guide portion 182 is reduced as much, reducing the area of the guide portion 182 in contact with the inner circumferential surface of the valve accommodation recess 175 to reduce friction resistance. Therefore, the check valve 180 may be moved more quickly, so that even when the pressure in the intermediate pressure chamber is slightly low at the time of restarting the compressor, the check valve 180 may be opened rapidly to quickly increase the pressure in the back-pressure space 144.

Meanwhile, in the embodiments described above, the check valve is moved only by a pressure difference, but in some cases, an elastic member may be provided on at least one of both sides of the check valve in a movement direction.

For example, when an elastic member 186 is provided on the first side surface of the check valve 180 as illustrated in FIG. 11A, the back-pressure hole 170 may be opened more quickly, and when the elastic member 186 Is installed on the second side surface of the check valve 180 as illustrated in FIG. 11B, the back-pressure hole 170 may be closed more quickly. When the elastic member 186 is installed on each of the first side surface 181 a and the second side surface 181 b of the check valve 180, noise such as impulsive noise that occurs during the process of opening and closing the check valve 180 may be absorbed to reduce overall noise due to the check valve 180.

Also, in the embodiments described above, the inner circumferential surface of the valve accommodation recess 175 has a circular shape and the guide portion 182 of the check valve 180 has a circular arc shape so that the check valve 180 is rotatably provided in the valve accommodation recess 175. However, the valve accommodation recess 175 and the check valve 180 may be engaged in the circumferential direction so that the check valve 180 may be moved in a predetermined path along the valve accommodation recess 175.

For example, as illustrated in FIG. 12, a guide recess 175 c may be formed on ab inner circumferential surface of the valve accommodation recess 175 so that the guide portion 182 of the check valve 180 may be inserted thereinto. The guide recess 175 c may be formed along a length direction of the valve accommodation recess 175. Accordingly, since the guide portion 182 is inserted into the guide recess 175 c of the valve accommodation recess 175, the check valve 180 is restrained in rotation in a circumferential direction and reciprocates along the same path.

Alternatively, as illustrated in FIG. 13, a guide recess 182 b may be formed on an outer circumferential surface of the guide portion 182 and a guide protrusion 175 d may be formed on ab inner circumferential surface of the valve accommodation recess 175. A guide protrusion 175 d of the valve accommodation recess 175 may be inserted into the guide recess 182 b of the guide portion 182 to restrict rotation of the check valve 180 in the circumferential direction. Of course, the guide projection and the guide recess may be formed at the guide portion and the valve accommodation recess, respectively.

When the guide recess 175 c or the guide protrusion 175 d is formed at the valve accommodation recess 175 in an axial direction as described above, the check valve 180 does not rotate in the circumferential direction, and thus, the behavior of the check valve 180 may be further stabilized.

In addition, the opening end 183 a of the communication recess 183 provided at the check valve 180 may be formed at a predetermined position, for example, at the lowermost position. When the electric compressor is installed in a lateral direction, if the oil in the compression chamber V is introduced into the valve accommodation recess 175 through the first back-pressure hole 171 together with the refrigerant, although a portion of the oil is present on the bottom side of the valve accommodation recess 175, the oil may be easily moved toward the second back-pressure hole 172 through the communication recess 183, and thus, the pressure in the back-pressure space 144 may be increased to a proper pressure more quickly.

Meanwhile, another embodiment of the electric compressor according to the present disclosure is as follows.

That is, in the above-described embodiments, the back-pressure hole is formed to penetrate through the first scroll and the frame, but the back-pressure hole may be formed to penetrate through the orbiting side disk plate portion of the second scroll. FIG. 14 is a cross-sectional view illustrating an example in which the back-pressure hole is formed to penetrate through the orbiting scroll according to the present disclosure.

As illustrated in the figure, a first back-pressure hole 271 is formed in the intermediate pressure chamber V toward the back-pressure space 144, and a valve accommodation recess 275 may be formed to be enlarged at one end (the second end toward the back-pressure space in the drawing) among both ends of the first back-pressure hole 271.

A stopper member 276 having a second back-pressure hole 272 may be inserted and coupled to an opening end of the valve accommodation recess 275. As a result, the check valve 180 reciprocates inside the valve accommodation recess 275. The stopper member 276 may be press-fit to the valve accommodation recess 275, may be engaged in a screw shape, or may be bonded using an adhesive or welding.

The second back-pressure hole 272, which forms a back-pressure passage together with the first back-pressure hole 271, may be formed at a position and have a size always communicating with the communication recess 183 of the check valve 180 as in the embodiment described above, and the opening and closing surface 181 of the check valve 180 is formed to be greater than an inner diameter of the first back-pressure hole 271 to opening and close the first back-pressure hole 271. Other basic configuration and corresponding operational effects of the check valve 180 and the back-pressure hole are similar to those of the embodiments described above. However, the present embodiment may be easily machined, compared with the embodiments described above. That is, in the embodiments described above, the back-pressure hole 170 is formed to penetrate through the first scroll 150 and the frame 140, and thus, a path of the back-pressure hole 170 is lengthened. Thus, it is difficult to form the back-pressure hole 170, and since the first back-pressure hole 171 and the second back-pressure hole 172 must be aligned accurately, high precision may be required in manufacturing the electric compressor. However, in the case of forming the back-pressure hole 270 at the disk plate portion 161 of the second scroll 160 as in the present embodiment, the length of the back-pressure hole 270 is short, and since the back-pressure hole 270 is formed at the one member, it is advantageous in manufacturing the electric compressor. Also, since the length of the back-pressure hole 170 is short, pressure drop of the refrigerant may be restrained as much, rapidly increasing the back pressure of the back-pressure space 144.

The foregoing embodiments and advantages are merely exemplary and are not to be considered as limiting the present disclosure. The present teachings may be readily applied to other types of apparatuses. This description is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. The features, structures, methods, and other characteristics of the exemplary embodiments described herein may be combined in various ways to obtain additional and/or alternative exemplary embodiments.

As the present features may be embodied in several forms without departing from the characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be considered broadly within its scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalents of such metes and bounds are therefore intended to be embraced by the appended claims. 

What is claimed is:
 1. An electric compressor comprising: a first scroll; a second scroll engaged with the first scroll and supported relative to the first scroll such that an orbiting motion of the second scroll relative to the first scroll forms a compression chamber between the second scroll and the first scroll; a frame fixed to a housing of the electric compressor and positioned on an opposite side of the second scroll from the first scroll with the second scroll interposed between the first scroll and the frame, the frame forming a back-pressure space between the frame and the second scroll, the second scroll being supported in a direction toward the first scroll by a pressure in the back-pressure space; a back-pressure passage connecting the compression chamber and the back-pressure space; and a valve member disposed in the back-pressure passage and selectively blocking movement of a fluid from the back-pressure space to the compression chamber.
 2. The electric compressor of claim 1, wherein the back-pressure passage includes a back-pressure hole, one end of the back-pressure hole being in fluid communication with the compression chamber and an opposite end of the back-pressure hole being in fluid communication with the back-pressure space, and a valve accommodation recess being in fluid communication with the back-pressure hole, the valve accommodation recess accommodating the valve member, and the valve member being configured as a check valve slidably movable inside the valve accommodation recess according to a pressure difference between the compression chamber and the back-pressure space.
 3. The electric compressor of claim 2, wherein the valve member includes a valve portion configured to open the back-pressure passage at a first position of the valve member and close the back-pressure passage at a second position of the valve member.
 4. The electric compressor of claim 3, wherein the valve portion has a first side surface, a second side surface, and a circumferential surface connecting the first side surface and the second side surface, and a diameter of the first side surface is greater than an inner diameter of the back-pressure hole and a diameter of the second side surface is smaller than an inner diameter of the valve accommodation recess.
 5. The electric compressor of claim 4, further comprising: an opening and closing surface formed on the first side surface of the valve portion such that at least a portion thereof is flat and formed with a diameter greater than the inner diameter of the back-pressure hole to block the back-pressure hole at the second position of the valve member; a support surface formed on the second side surface of the valve portion and formed to contact a side surface of the valve accommodation recess at the first position of the valve member; and a communication recess formed to a predetermined depth on the support surface, opened to the circumferential surface of the valve portion, and at least partially overlapping the back-pressure hole facing the second side surface.
 6. The electric compressor of claim 5, wherein the valve member further comprises at least one guide portion configured to guide the valve portion from the first position to the second position, and the at least one guide portion extends in a radial direction toward an inner circumferential surface of the valve accommodation recess from the circumferential surface of the valve portion.
 7. The electric compressor of claim 6, wherein the at least one guide portion includes two guide portions protruding in a radial direction from portions of the circumferential surface of the valve portion, and the communication recess is opened to the circumferential surface of the valve portion positioned between the two guide portions.
 8. The electric compressor of claim 7, wherein the communication recess has at least two end portions opened to the circumferential surface of the valve portion.
 9. The electric compressor of claim 6, wherein the at least one guide portion includes a plurality of guide portions, and respective guide portions of the plurality of guide portions are formed at equal intervals along a circumferential direction of the circumferential surface of the valve portion.
 10. The electric compressor of claim 6, wherein the at least one guide portion is a single guide portion, and a subtended angle of the single guide portion is greater than or equal to approximately 180°.
 11. The electric compressor of claim 6, wherein the at least one guide portion has a thickness approximately equal to or smaller than a thickness of the valve portion.
 12. The electric compressor of claim 6, wherein at least one guide recess is formed on an inner circumferential surface of the valve accommodation recess and a respective one of the at least one guide portion is inserted into the at least one guide recess and restrained by the at least one guide recess from movement in a circumferential direction.
 13. The electric compressor of claim 1, wherein an elastic member is disposed on any one of opposite sides of the valve member in a direction of movement of the valve member.
 14. The electric compressor of claim 1, wherein the back-pressure passage includes: a first back-pressure hole formed in the first scroll and in fluid communication with the compression chamber; and a second back-pressure hole formed in the frame and in fluid communication with the back-pressure hole, wherein the first back-pressure hole and the second back-pressure hole are in fluid communication with each other; and a valve accommodation recess accommodating the valve member is formed at least in part in at least one of the first scroll or the frame.
 15. The electric compressor of claim 1, wherein the back-pressure passage is formed penetrating through the second scroll and in fluid communication with the back-pressure space, a valve accommodation recess is formed in a middle portion of the back-pressure passage, a stopper member configured for limiting movement of the valve member is inserted in and coupled to the valve accommodation recess, and the stopper member includes a back-pressure hole in fluid communication with the back-pressure passage.
 16. An electric compressor comprising: a frame; a first scroll fixedly supported in the frame; a second scroll pivotably supported relative to the frame and the first scroll and engaged with the first scroll; a compression chamber formed between the first scroll and the second scroll and configured to decrease in volume from an outer portion of the compression chamber toward an inner portion of the compression chamber upon relative movement between the first scroll and the second scroll to compress a fluid contained within the compression chamber; a back-pressure space formed between the second scroll and the frame, wherein pressure within the back-pressure space acts on the second scroll and supports the second scroll toward the first scroll; a back-pressure flow path connecting the compression chamber and the back-pressure space; a valve accommodation recess formed in a middle portion of the back-pressure flow path; and a check valve disposed in the valve accommodation recess and configured to block the back-pressure flow path when a pressure in the back-pressure space is higher than a pressure in the compression chamber.
 17. The electric compressor of claim 16, wherein the check valve includes a valve portion, the valve portion formed to include a diameter greater than an inner diameter of the back-pressure flow path and smaller than an inner diameter of the valve accommodation recess, at least a portion of one side surface of the valve portion is formed substantially flat to selectively establish close contact with one side of the valve accommodation recess and block the back-pressure flow path in a first position of the valve portion, and the other side surface of the valve portion includes a communication recess configured to open the back-pressure flow path when the other side surface of the valve portion establishes close contact with the other side of the valve accommodation recess in a second position of the valve portion.
 18. The electric compressor of claim 17, wherein the check valve further includes at least one guide portion in slidable contact with an inner circumferential surface of the valve accommodation recess, and the at least one guide portion protrudes from a circumferential surface of the valve portion along a circumferential direction of the valve portion.
 19. An electric compressor comprising: a frame; a fixed scroll supported in the frame; an orbiting scroll pivotably supported relative to the frame and the fixed scroll, engaged with the fixed scroll, and interposed between the fixed scroll and the frame; a compression chamber including at least two variable volumes formed between the fixed scroll and the orbiting scroll, wherein orbital movement of the orbiting scroll relative to the fixed scroll causes the variable volumes of the compression chamber to alternately increase in volume to draw fluid into the compression chamber and decrease in volume to compress the fluid contained within the compression chamber and discharge the fluid; a back-pressure space formed between the orbiting scroll and the frame, wherein pressure of fluid within the back-pressure space acts on a first side of the orbiting scroll opposite from a second side of the orbiting scroll engaged with the fixed scroll, the pressure pushing the orbiting scroll in a direction toward the fixed scroll; a back-pressure passage connecting the compression chamber and the back-pressure space; a valve accommodation recess formed in a portion of the back-pressure passage; and a check valve disposed in the valve accommodation recess and configured to move to a position in which the check valve blocks the back-pressure passage when a pressure in the back-pressure space is higher than a pressure in the compression chamber.
 20. The electric compressor of claim 19, wherein: the back-pressure passage is formed as one of a combination of through holes formed in the fixed scroll and the frame, or a single through hole formed in the orbiting scroll. 